Need mouse advice ASAP PLEASE

OK so I bought some lovely mice the other day at a pet produce store, but turns out one of them had babies tonight (the cashier said that they couldn’t guarantee that they weren’t pregnant, so i’m guessing that they were all stabled together or something before they were split into two different cages or they don’t know originally where they had come from.)

Anyway, please I need help on what to do now because I am not a breeder! They look fine and I can see their milk bands/spots and I have moved the other mice she was with to a separate cage but kept that cage close

Also please don’t bombard me with any ‘you should have known she was pregnant’ or anything like that. I need to know what to do now as this is my and my pets priority!

I have put some towels over the baby end of the cage, put in some water and food for the mother and some fresh newspaper for extra bedding.

Do I keep her and the babies separate from the other mice?
Do I leave them in that cage until they are weaned and try to return them back to the store or earlier?
Do I need to provide any fibre to the mother or extra nutrients?

I have looked briefly at what I should do

I will post pictures momentary

please help me out?